Furnace



July 22, 194:7I E. E.-RoBERTsoN FURNACE Filed Feb. l, 1946 mnwn .....1...H.....L.H..r......b1.- Huw... M ON N m O w- N.- w v INVENTOR ELMER E. ROBERTSON ATTORNEY Patented July 22, 1947 FUnNAcE Elmer E. Robertson, Harbor City, Calif. Application February 1,1946, serial No. 644,837

6 Claims.

This invention relates to a furnace for expanding mineral materials such as perlite, vermiculite,

and the like.

IOne object of my invention is to provide a furnace in which puing minerals such as perlite and vermiculite may be expanded by heat. Another object is to provide a furnace apparatus in rwhich particles of puffing minerals may be repeatedly subjected to the heat of a llame while Asuspended in a gas medium. Still another object is to provide means for continuously puffing perlite, vermiculite, and the like.

My invention will be understood from the following description, reference being made to the accompanying drawings in which:

Fig, 1 is a top plan view of my furnace structure;

Fig. 2 is a side elevational view of the same; and

Fig. 3 is a cross-sectional View taken on the line 3&3 of Fig. 1.

Referring to the drawings, a rectangular elongated box structure forms the casing II for my furnace, this casing being pivotally mounted on trunnions I2 disposed intermediate the ends of the furnace and having adjustable end supporting members I3 arranged so that the general slope of the furnace may be. adjusted as desired. The heating chamber consists of a tubular conduit I4 which is arranged in a horizontal zig-zag path from one end of the furnace to the other -by the joining of cylindrical pipe segments I5 whose ends I6 are joined so that adjacent segments are at angles of from 120 to 140, with provision for the incorporation of gas burners I1 at the bends, the burners being directed near the center of the conduit and in the direction of the successive segments. A front gas burner I8 is provided in the furnace entrance end I9. Granular mineral material such as perlite or vermiculite is fed into the vertically arranged funnel which directs the granular material in front of the burner I8 where the gases vfrom the burner disperse the mineral particles, at the same time heating them and carrying the material forward to the first segment of the tubular conduit, at which point another burner Il is directed into the next segment, where the gases added by the rburner cause further dispersion and heating of the granular materials. This is repeated at the several elbows IBA in the conduit IM, as many ofthe segments and gas burners being provided as required by the nature of the material to be heated and expanded.

In some cases, it is desirable to produce'additional spiral turbulence and segregation of the suspended partly expanded mineral in the gases,

2 and to slow up the velocity of advance, which may be accomplished by introducing a helical section 2I in place of one or more of =the straight segments I5. As shown, three complete helical loops in the conduit are' provided but this number may be increased or decreased as desired to give the required effect. The heavier incompletely expanded particles are segregated from the completely expanded material by this centrifugal action so that they may be acted upon by the subsequent heating of later burners. The expanded' or exploded mineral material such as perlite is collected at the exit end 22 of the conduit by the use of any convenient form of collecting apparatus C such as cyclone collectors, bailled chambers, etc.

The mineral perlite is peculiar in its response to heating in that when it reaches a certain critical temperature in the neighborhood of l600 to 1700 F., it suddenly expands to many times its original volume. Only that portion of the mineral particle is thus expanded which has reached the critical temperature. This critical temperature varies somewhat for material from one source of mineral to another since perlite is not a mineral of definite composition. 'I'he portion of the mineral particle which when heated does not attain its critical temperature for expanding remains as a hard granule, and a mixture of highly expanded very light material along with heavy particles of unexpanded material is undesirable in the use of the material. This dimculty in expanding the material has been overcome by the yuse of my furnace which subjects the particles to the flames of gas burners arranged at positions in the elbows to most effectively subject the gascarried particles to further heating so that if a particle is not completely expanded in the first stage, it has a good opportunity of being again heated to the critical temperature at subsequent burner positions.

The conduit I4 is preferably made of suitable metal in the form of smooth surfaced pipe to which themineral does not adhere such as stainless steel or glazed high temperature porcelain.

I have found that if the conduit is of granular rough structure such as of nre brick or the like, that the expanded perlite tends to adhere and build up in the interior of the furnace and prevents the further use, without frequently shutting down to clean out obstructions. The furnace conduit may be suitably insulated inside the case I I either by dead air space or by the use of standard insulating refractory materials placed around the tubes.

In order to control the flow of gases and material through the furnace tube, I nd it desirable to be able to adjust the inclination of the furnace from the horizontal position shown in the drawings, and for this purpose have mounted the case I l on the trunnions Il and provided adjustable end supporting means so that either end of the furnace may be raised or lowered to attain the desired effect.

I claim: y i p l. In a furnace for heating a granular material held in suspension in combustion gases, a substantially horizontally disposed zigzas tubular conduit adapted to carry a stream of heated gases with suspended mineral particles from a feed end to a delivery end; and burner means directed into said conduit at two or more of the angles thereof.

2. In a furnace for heating a granular material heid in suspension in combustion gases, a subnanf tially horizontally disposed zigzag conduit conrprising segments of tubing joined together at their ends at obtuse angular positions, adapted to carry a stream of heated gases with suspended mineral particles from a feed end to a delivery end; burner means directed into successive segments of said'4 conduit at their entrance ends for said stream of gas; and means for introducing granular material into the feed end of said furnace.

3. In a furnace `for heating an intumescing granular material held in suspension in combustion gases, a substantially. horizontally disposed zigzag tubular conduit comprising segments of tubing joined together at their ends at obtuse angular positions, adapted to carry a stream of heated gases with suspended mineral particles from a feed end to a delivery end; burner means directed into successive segments of said conduit at their entrance ends for said stream of gas; means for introducing granular material into the feed end of said furnace;` and means in a later segment of the conduit to segregate unexpanded and heavy particles of mineral from the fully intumesced particles.

4. In a. furnace for heating an intumescin'g 4 granular material held in suspension in combus tion gases, a substantially horizontally disposed Zim tubular conduit adaptedtocarryastream of heated gases with suspended mineral particles from a feed end to a delivery end; burner means directed into said conduit at the angles thereof; means for feeding the granular material into the feed end of said furnaeefmeans in a Interpol-tion of the conduit to segregate unexpanded and heavy particles of mineral from the fully intumesced particles; and means to vary the general slope of said furnace.

5. In a furnace for heating an intumescing granular material held in suspension in combustion gases, a substantially horizontally disposed zigzag tubular conduit comprising segments of tubing joined together attheir ends at obtuse angles, adapted to carry a stream of heated gases with suspended mineral particles from a feed end to a delivery end; burner means directed into said conduit at two or more of the angles thereof;

and means in a later portion of the conduit adapted to segregate unexpanded and heavy partiels of mineral from the fully expanded particles consiitng of helical turns in a segment of said oond 6. In a furnace, for heating an intumescing granular material held in suspension in combustion gases, a substantially horizontally disposed zigzag tubular conduit comprising segments of tubing joined together at their ends at obtuse angles, adapted to carry a stream of heated gases with suspended mineral prticles from a feed end to a delivery end; burner means directed into said conduit at two or more of the angles thereof;

A means for feeding granular material into the feed end of said furnace; a helical coiled tubing forming one segment of said conduit, said coiled tubing being adapted to segregate unexpanded and heavy particles of mineral from the fully expanded particles; and means to vary the general slop'e of said furnace.

E. ROBERTSON. 

